On the relationship between energy input to the ionosphere and the ion outflow flux under different solar zenith angles

Earth, Planets and Space

Naritoshi Kitamura¹  Kanako Seki¹  Kunihiro Keika¹  Robert J. Strangeway²  Yukitoshi Nishimura³  Tomoaki Hori⁴  Masafumi Hirahara⁴  Eric J. Lund⁵  Lynn M. Kistler⁶ 

[1]Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan

[2]Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA, USA

[3]Department of Electrical and Computer Engineering and Center for Space Physics, Boston University, Boston, MA, USA

[4]Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Japan

[5]Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA

[6]College Brook Scientific, Durham, NH, USA

[7]Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA

[8]Department of Physics, University of New Hampshire, Durham, NH, USA

关键词: Auroral ion outflow;    Polar ionosphere;    Auroral precipitation;    FAST satellite;    Cleft ion fountain;    Ion conics;    Ion beams;   

DOI  :  10.1186/s40623-021-01532-y

来源: Springer

【 摘 要 】

The ionosphere is one of the important sources for magnetospheric plasma, particularly for heavy ions with low charge states. We investigate the effect of solar illumination on the number flux of ion outflow using data obtained by the Fast Auroral SnapshoT (FAST) satellite at 3000–4150 km altitude from 7 January 1998 to 5 February 1999. We derive empirical formulas between energy inputs and outflowing ion number fluxes for various solar zenith angle ranges. We found that the outflowing ion number flux under sunlit conditions increases more steeply with increasing electron density in the loss cone or with increasing precipitating electron density (> 50 eV), compared to the ion flux under dark conditions. Under ionospheric dark conditions, weak electron precipitation can drive ion outflow with small averaged fluxes (~ 107 cm−2 s−1). The slopes of relations between the Poynting fluxes and outflowing ion number fluxes show no clear dependence on the solar zenith angle. Intense ion outflow events (> 108 cm−2 s−1) occur mostly under sunlit conditions (solar zenith angle < 90°). Thus, it is presumably difficult to drive intense ion outflows under dark conditions, because of a lack of the solar illumination (low ionospheric density and/or small scale height owing to low plasma temperature).Graphical abstract

【 授权许可】

CC BY